A regulator of the described type is disclosed in U.S. Pat. No. 2,768,643, and includes a casing which mounts a valve positioned between inlet and outlet gas passages, and a diaphragm clamped within the casing so as to be movable to adjust the size of the opening of the valve. The movement of the diaphragm, and thus the pressure of the gas being discharged, are controlled by a manually adjustable screw, which controls the loading of a spring which engages the diaphragm.
U.S. Pat. No. 4,516,595 issued to Acomb discloses a similar regulator which includes a plunger positioned to isolate the diaphragm from the valve seat in response to a spontaneous ignition or overpressure within the regulator body upstream of the diaphragm. By immediately closing off the diaphragm chamber, the plunger essentially prevents ignition of the diaphragm, purportedly substantially reducing the potential for a sustained combustion within the regulator. The plunger is retained by a separate threaded member which is screwed onto the valve body.
An improvement in the type of regulator disclosed by Acomb is described in pending patent application Ser. No. 08/585,802 filed on Jan. 16, 1996, now U.S. Pat. No. 5,711,340 issued to Gusky et al., commonly owned with the present application, and entitled "Gas Pressure Reducing Regulator", the entire disclosure of which is incorporated herein by reference. The regulator includes a back-up plate which overlies one side of the flexible diaphragm, and a spring which engages the back-up plate so as to bias the diaphragm assembly in a direction to tend to open the valve to allow gas flow to the outlet of the regulator. The back-up plate includes a vent opening extending axially therethrough, and the closure cap which contains the spring and back-up plate includes a vent for venting the inside of the cap to the atmosphere. Thus, in the event of an overpressure in the chamber below the diaphragm resulting for example from ignition of the gas passing through the regulator and such overpressure reaches the flexible diaphragm, the flexible diaphragm is able to rupture and release the pressure through the vent opening in the back-up plate and then through the vent in the closure cap so that the pressure is released to the atmosphere. The regulator also includes a plunger for isolating the diaphragm from the valve seat, the plunger being retained by a threaded plunger-retaining member which is screwed into the valve body.
While the regulator described in the Gusky patent provides protection against regulator burn-out, there is still room to further improve this aspect of the regulator's performance. Additionally, the inclusion of the plunger-retaining member complicates the design of the valve body and requires additional manufacturing and assembly operations.